[info] Using makefile-style concurrent boot in runlevel 2. [....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.360784][ T1666] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 37.018616][ T1706] random: sshd: uninitialized urandom read (32 bytes read) [ 37.101044][ C1] random: crng init done Warning: Permanently added '10.128.0.66' (ECDSA) to the list of known hosts. executing program [ 43.802465][ T12] usb 1-1: new high-speed USB device number 2 using dummy_hcd [ 44.042447][ T12] usb 1-1: Using ep0 maxpacket: 8 [ 44.162563][ T12] usb 1-1: config 0 has an invalid interface number: 219 but max is 0 [ 44.171068][ T12] usb 1-1: config 0 has no interface number 0 [ 44.177435][ T12] usb 1-1: config 0 interface 219 altsetting 0 endpoint 0xF has an invalid bInterval 0, changing to 7 [ 44.188695][ T12] usb 1-1: config 0 interface 219 altsetting 0 endpoint 0x83 has an invalid bInterval 0, changing to 7 [ 44.199878][ T12] usb 1-1: New USB device found, idVendor=0694, idProduct=0001, bcdDevice=eb.88 [ 44.209050][ T12] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 44.218517][ T12] usb 1-1: config 0 descriptor?? [ 44.482520][ T12] legousbtower 1-1:0.219: LEGO USB Tower firmware version is 129.136 build 65535 [ 44.497155][ T12] legousbtower 1-1:0.219: LEGO USB Tower #-160 now attached to major 180 minor 0 [ 45.742647][ T1722] usb 1-1: LEGO USB Tower reset control request failed [ 45.750443][ T12] usb 1-1: USB disconnect, device number 2 [ 45.760230][ T12] [ 45.762592][ T12] ====================================================== [ 45.770293][ T12] WARNING: possible circular locking dependency detected [ 45.777326][ T12] 5.3.0-rc7+ #0 Not tainted [ 45.781805][ T12] ------------------------------------------------------ [ 45.788827][ T12] kworker/0:1/12 is trying to acquire lock: [ 45.794694][ T12] 0000000098630ee4 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230 [ 45.803176][ T12] [ 45.803176][ T12] but task is already holding lock: [ 45.810518][ T12] 00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300 [ 45.819344][ T12] [ 45.819344][ T12] which lock already depends on the new lock. [ 45.819344][ T12] [ 45.829739][ T12] [ 45.829739][ T12] the existing dependency chain (in reverse order) is: [ 45.838734][ T12] [ 45.838734][ T12] -> #1 (open_disc_mutex){+.+.}: [ 45.845839][ T12] __mutex_lock+0x158/0x1360 [ 45.850927][ T12] tower_open+0xce/0x9b0 [ 45.855688][ T12] usb_open+0x1df/0x270 [ 45.860348][ T12] chrdev_open+0x219/0x5c0 [ 45.865262][ T12] do_dentry_open+0x494/0x1120 [ 45.870522][ T12] path_openat+0x1430/0x3f50 [ 45.875693][ T12] do_filp_open+0x1a1/0x280 [ 45.880692][ T12] do_sys_open+0x3c0/0x580 [ 45.885923][ T12] do_syscall_64+0xb7/0x580 [ 45.890951][ T12] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 45.897342][ T12] [ 45.897342][ T12] -> #0 (minor_rwsem){++++}: [ 45.904132][ T12] __lock_acquire+0x1f7c/0x3b50 [ 45.909571][ T12] lock_acquire+0x127/0x320 [ 45.914947][ T12] down_write+0x92/0x150 [ 45.919722][ T12] usb_deregister_dev+0x95/0x230 [ 45.925249][ T12] tower_disconnect+0xa8/0x300 [ 45.930617][ T12] usb_unbind_interface+0x1bd/0x8a0 [ 45.936312][ T12] device_release_driver_internal+0x42f/0x500 [ 45.942874][ T12] bus_remove_device+0x2dc/0x4a0 [ 45.948316][ T12] device_del+0x420/0xb10 [ 45.953159][ T12] usb_disable_device+0x211/0x690 [ 45.958680][ T12] usb_disconnect+0x284/0x8d0 [ 45.964045][ T12] hub_event+0x1454/0x3640 [ 45.968958][ T12] process_one_work+0x92b/0x1530 [ 45.975517][ T12] worker_thread+0x96/0xe20 [ 45.980517][ T12] kthread+0x318/0x420 [ 45.985182][ T12] ret_from_fork+0x24/0x30 [ 45.990111][ T12] [ 45.990111][ T12] other info that might help us debug this: [ 45.990111][ T12] [ 46.000430][ T12] Possible unsafe locking scenario: [ 46.000430][ T12] [ 46.008781][ T12] CPU0 CPU1 [ 46.014232][ T12] ---- ---- [ 46.019583][ T12] lock(open_disc_mutex); [ 46.023993][ T12] lock(minor_rwsem); [ 46.030562][ T12] lock(open_disc_mutex); [ 46.037657][ T12] lock(minor_rwsem); [ 46.041702][ T12] [ 46.041702][ T12] *** DEADLOCK *** [ 46.041702][ T12] [ 46.049903][ T12] 6 locks held by kworker/0:1/12: [ 46.055262][ T12] #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at: process_one_work+0x827/0x1530 [ 46.065493][ T12] #1: 0000000054d9228f ((work_completion)(&hub->events)){+.+.}, at: process_one_work+0x85b/0x1530 [ 46.076276][ T12] #2: 00000000f97c245e (&dev->mutex){....}, at: hub_event+0x17c/0x3640 [ 46.084592][ T12] #3: 0000000035f038d2 (&dev->mutex){....}, at: usb_disconnect+0x91/0x8d0 [ 46.093243][ T12] #4: 00000000accb22e6 (&dev->mutex){....}, at: device_release_driver_internal+0x23/0x500 [ 46.103365][ T12] #5: 00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300 [ 46.112466][ T12] [ 46.112466][ T12] stack backtrace: [ 46.118354][ T12] CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.3.0-rc7+ #0 [ 46.125913][ T12] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 46.135978][ T12] Workqueue: usb_hub_wq hub_event [ 46.141061][ T12] Call Trace: [ 46.144332][ T12] dump_stack+0xca/0x13e [ 46.148779][ T12] check_noncircular+0x345/0x3e0 [ 46.153706][ T12] ? print_circular_bug+0x1b0/0x1b0 [ 46.158923][ T12] ? kfree_const+0x51/0x60 [ 46.163334][ T12] ? device_destroy+0x98/0xd0 [ 46.168002][ T12] ? usb_deregister_dev+0x89/0x230 [ 46.173092][ T12] ? tower_disconnect+0xa8/0x300 [ 46.178005][ T12] ? graph_lock+0x80/0x180 [ 46.182485][ T12] ? hlock_class+0x120/0x120 [ 46.187059][ T12] ? mark_lock+0xbc/0x1130 [ 46.191467][ T12] ? debug_check_no_obj_freed+0x20f/0x443 [ 46.197171][ T12] ? find_first_zero_bit+0x94/0xb0 [ 46.202283][ T12] __lock_acquire+0x1f7c/0x3b50 [ 46.207123][ T12] ? mark_held_locks+0x9f/0xe0 [ 46.211873][ T12] ? lockdep_hardirqs_on+0x379/0x580 [ 46.217322][ T12] ? mark_held_locks+0xe0/0xe0 [ 46.222092][ T12] ? lockdep_hardirqs_on+0x379/0x580 [ 46.227366][ T12] lock_acquire+0x127/0x320 [ 46.231860][ T12] ? usb_deregister_dev+0x95/0x230 [ 46.237027][ T12] down_write+0x92/0x150 [ 46.241460][ T12] ? usb_deregister_dev+0x95/0x230 [ 46.246596][ T12] ? __down_timeout+0x2d0/0x2d0 [ 46.251607][ T12] ? root_device_unregister+0x80/0x80 [ 46.257111][ T12] usb_deregister_dev+0x95/0x230 [ 46.262033][ T12] tower_disconnect+0xa8/0x300 [ 46.266788][ T12] usb_unbind_interface+0x1bd/0x8a0 [ 46.272218][ T12] ? usb_autoresume_device+0x60/0x60 [ 46.277490][ T12] device_release_driver_internal+0x42f/0x500 [ 46.283540][ T12] bus_remove_device+0x2dc/0x4a0 [ 46.288471][ T12] device_del+0x420/0xb10 [ 46.292946][ T12] ? __device_links_no_driver+0x240/0x240 [ 46.298658][ T12] ? usb_remove_ep_devs+0x3e/0x80 [ 46.303666][ T12] ? remove_intf_ep_devs+0x13f/0x1d0 [ 46.308943][ T12] usb_disable_device+0x211/0x690 [ 46.313961][ T12] usb_disconnect+0x284/0x8d0 [ 46.318635][ T12] hub_event+0x1454/0x3640 [ 46.323054][ T12] ? find_held_lock+0x2d/0x110 [ 46.327811][ T12] ? mark_held_locks+0xe0/0xe0 [ 46.332590][ T12] ? hub_port_debounce+0x260/0x260 [ 46.337681][ T12] process_one_work+0x92b/0x1530 [ 46.342597][ T12] ? pwq_dec